answer your door with a smart phone watching the wifi video at door bell

courtesy by: google images

Answer your door with a smart phone
The door bell in build camera will provide the video "who is outside your door".
So that door bell gives the control, convenience and safety. whether you are at home or away from your home. You can know the person and answer.
you can receive an alert when he doesn't press the bell.
shop and courtesy by: door bell